It was random, but out of several foreign researchers planning to attend the annual Black Hat security conference in Las Vegas this week, Thomas Dullien (better known as "Halvar Flake") was denied access at the border. Dullien happened to enter the United States amid heightened security among airport screeners at the Detroit airport. Dullien reportedly told Black Hat officials that as he was boarding the plane back to Germany, a screener mentioned Detroit was experiencing a crackdown following an episode earlier at that airport. That's the speculation on the day after Dullien's security class for the annual Black Hat Training in Las Vegas was canceled. Dullien remains in Berlin, trying to get a three-day business visa back to the United States in the hopes he can attend the latter half of the conference.

Meanwhile, Black Hat officials worked swiftly on Sunday to relocate the 20 students left without an instructor. Black Hat Director Jeff Moss said they contacted everyone registered for Dullien 's class via e-mail and reassigned them into existing classes. Still, on Monday morning, there were a handful of students who didn't know about the class cancellation, or still hadn't decided on a replacement class.

Moss said that the original agreement between Black Hat and Dullien was not between his company but with him as an individual. That fact that Black Hat, a U.S. company, would pay Dullien directly apparently violated the visa waiver he'd signed. Moss said Black Hat drew up a new contact Sunday afternoon, but by then Dullien was on a plane back to Germany.

About the author

As CNET's former resident security expert, Robert Vamosi has been interviewed on the BBC, CNN, MSNBC, and other outlets to share his knowledge about the latest online threats and to offer advice on personal and corporate security.
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Discuss Detroit crackdown blocks security professional's entry into the U.S.